This invention relates to ureteral stents, and more particularly to a novel infusion stent system that permits infusion of fluid at any selected location in the stent.
Ureteral stents have long been used for such purposes as draining fluid from the renal pelvis to the bladder, and for providing support to a collapsed or restricted ureter.
Ureteral stents may also be used in conjunction with extracorporeal shock wave lithotropsy (ESWL), a procedure for pulverizing kidney stones without surgery. During ESWL, a device known as a lithotripter emits high frequency electrohydraulic waves that destroy the kidney stones. The waves are administered to a patient submerged in a bath of water. Electrodes are attached to brass disk behind the patient and when the lithotripter is activated, up to 1500 electrohydraulic waves travel through the water to crush the stone to infinitesimal fragments that the patient can then pass naturally. The natural passing of the stone is facilitated with a stent.
One known stent used in ESWL procedures, designated the Kwart Retro-Inject Stent manufactured by Cook Urological of Spencer, Ind., and identified by Model Nos. 003600 and 003700, includes a system comprising a stent, a solid core wire guide, an inserter and a release sleeve. The stent is normally coiled or looped at opposite ends and includes perforations along the length of the stent.
In using the Kwart Retro-Inject Stent Set, the wire guide is positioned in the patient and the stent is pushed on the wire guide into the renal cavity by the inserter. The inserter is pushed into the stent a distance of approximately 5 mm thus forming a tubular extension of the stent.
After the stent is positioned in the patient, the wire guide is removed to allow the stent coils or loops to re-form in the renal pelvis. Fluid is injected through the inserter and into the stent during an ESWL procedure to disclose stones or stone fragments for targeting. The stent can also be left in place for internal drainage.
One of the problems with the Kwart Retro-Inject stent system is that infusion of fluid through the inserter cannot be specifically directed outwardly of the stent at any selected portion of the stent. Fluid is injected into one end of the stent through the inserter. The injected fluid traverses the stent exiting through any or all of the openings in the stent.
Another known stent set manufactured by Cook Urological under the designation Wegenke Exchange/Retrograde Ureteral Stent Set Model No. 0046, is also unable to direct fluid to any selected part of the stent. Fluid injected into one end of the stent traverses the stent to whatever openings are provided therein.
Still another known stent set made by Van-Tec of Spencer, Ind., under Model No. SI1726, also requires injection of fluid through one end of the stent for passage within the stent to any available openings in the stent or an open end of the stent. Since fluid can only be injected through an end of the stent, fluid infusion cannot be focused outwardly of the stent at any one location in the stent if openings are distributed along the length of the stent.
It is thus desirable to provide an infusion stent system which can be used to infuse fluid at any selected location in a stent and which also has optimal drainage capability when the stent is left as an indwelling member.